Methicillin resistant Staphylococcus aureus (MRSA) has become a serious source of life-threatening hospital infections and increasingly community acquired infections. As our current treatments for MRSA infections are losing efficacy, there is an urgent need for new antibiotics to cope with this problem. A recently discovered metabolite, bacillithiol (BSH), has been shown to be present in S. aureus and Bacillus spp., but is absent in human or other higher organisms. The specific aims of the research are to identify and characterize enzymes involved in BSH metabolism, such as bacillithiol disulfide reductase, and to elucidate S. aureus BSH dependent xenobiotic detoxification pathways. The results of these studies will elaborate the functions of BSH and will establish whether BSH metabolism is a suitable target for staphylococcal drug development. As thiols are known to be involved in the development of drug resistance, this research may provide insight into intrinsic drug resistance in S. aureus. PUBLIC HEALTH RELEVANCE: Staphylococcus aureus is a major human pathogen capable of causing a range of diseases from superficial skin infections to deadly septicemia and toxic shock syndrome. The increase in prevalence of methicillin resistant S. aureus (MRSA) strains and the advent of vancomycin resistant MRSA strains makes it imperative that new drug targets be identified and characterized. Drug detoxification and subsequent resistance pose serious problems to the further treatment of bacterial infections. Thiols have been shown to play a key role in detoxification and thus mechanisms of drug resistance and detoxification in S. aureus be carefully scrutinized in order to find ways to overcome these mechanisms. In this proposal, we identify and characterize potential new drug targets and explore the way S. aureus becomes resistant to existing drugs.